High energy gaseous discharge device



Feb. 16, 1960 v. JOSEPHSON 2,925,512

' HIGH ENERGY GASEOUS DISCHARGE DEVICE Filed Oct. 8, 1957 9' R "a m x t 2 Q k Q i z z Q v Q Q i t Q 1 a h m H Q (*5 S El '6\ Q I 6 4 vk w w INVENTOR. Vernal Josephson firw 2,925,512 HIGH ENERGY GASEOUS DISCHARGE DEVICE Vernal Josephson, Palos Verdes Estates, Calif., assignor to the United States of America as represented bythe United States Atomic Energy Commission Application October 8, 1957,'Serial No. 689,017 3 Claims. 01. 313-155 This invention relates to apparatus for producing high energy gas ionization discharges, i.e., plasmas. Such apparatus has numerous uses such as in laboratory researches in the behavior of very hot plasmas, for the attainment of basic information in the atomic and kinetic behavior of atoms under such conditions. In addition, a high energy gaseous discharge produces an exceedingly intense, and closely controlled in time, flash of light of particular value for high speed photography purposes.

The temperature of the plasma produced by a high second magnetic field aligned with the direction of discharge.

Apparatus for producing high energy discharges forthe laboratory studies or other purposes above enumerated have hitherto been made of a vitreous material such as quartz, ceramic, porcelain or glass. It has been found that contamination of the gas being ionized and heated results from the use of such materials evaporating during the discharge. In fact, due to the necessity of preserving high purity in a particular gas being ionized, contamination from the vessel in effect makes the use of such prior art devices, in many cases, single shot devices. Also, there are circuit considerations which .limit the vessel wall thickness to a value which seriously restricts the use of the vessel to moderate energies because of its susceptibility to breakage under the resulting shock.

It is the prime purpose of the present invention to provide a high energy gaseous discharge device which eliminates the shortcomings of the prior art devices and which, in addition, provides a number of advantages not obtained in such prior art devices. Further objectives and advantages will become apparent from the following description taken with reference to the drawing made a part of this specification. The single figure of the drawing shows a preferred embodiment of a device in accordance with this invention.

Referring to the drawing, an elongated metal container or envelope 11 is provided for confining a gas and the resulting discharges. The vessel 11 need not be made of metal insofar as contamination of the gas is concerned for the reason that it is shielded from the discharge by other structure in a manner which will presently become apparent. However, there is an advantage in the use of a high conducting outer container 11 from the viewpoint of circuitry considerations.

A pair of main discharge electrodes 19 and 21 are disposed symmetrically with respect to the median line of envelope 11. Electrode 21 is directly electrically connected to one end of container 11. Electrode 19 is insulatingly supported by insulating members 23 in the opposite end of the container 11. The electrodes 19 and 21 are for the purpose of establishing an ionized discharge along the direction of elongation of envelope l1.

- United States Patent is provided to surround the path of the ionized column.

This conducting shield is-provided by a helix of a high conducting metal strap such as, for example, copper ribbonhaving such a plurality of turns as to constitute a solenoid, and having the ends thereof connected to the respective electrodes 12 and 21. Adjacent turns of the solenoid must be sufficiently spaced so as to prevent electrical discharge thereacross due to the potential applied to the solenoid. To the end that the plasma zone will be entirely confined by metallic surfaces, a second helix 15 of corresponding pitch to that of the first helix 13 is provided over and in staggered relation with respect,

to the first helix. It is also necessary that the outer helix 15 be supported on inner helix 13 in an insulated fashion and accordingly insulated ribbon elements 17 are provided between the two solenoids. The insulating material is out of the direct path of impingement of the ions and so does not result in contamination of the gas being heated. The high conductivity of the metallic faces prevents the evaporating of the metal and accordingly eliminatesthe deleterious contamination of the gas.

In order to provide the stabilizing longitudinal magnetic field a source of potential 24 is provided and is connected through the walls of envelope 11 to one end of the inner solenoid through jumper 33 and through electrode 19 and jumper 35 to the other end of the solenoid. In operation this source of potential would be impressed across the solenoid by the closure of switch 25 prior to the main discharge through the gas across electrodes 19 and 21. The main discharge is generated by the closure of switch 29 which is connected in series with a high capacitance,'high potential capacitor 27. The connecting circuit between capacitor 27 and the gaseous column is provided by envelope 11, electrode 21, electrode 19,

and switch 29. The helical form of solenoid 13 has considerably higher inductance than that of the ionized path between electrodes 19 and 21, and, therefore, provides substantially an open circuit with respect to the main discharge potential.

A benefit of considerable importance resulting from the use of metal for the envelope is that the envelope together with the ion discharge provide in effect a co-axial line of low impedance. This admits of a very high amplitude of current discharge as well as the conservation of energy by the absence of an external magnetic field.

Tests made on such a tube with the solenoid inductance being approximately five times the total discharge circuit inductance and with an initial 500 volts per turn from the main discharge potential supply 27 shows no deterioration in the visual pinch occurring in the tube. The time for the gas to break down and conduct was much shorter and more constant than in glass discharge tubes. One example of a practical embodiment is as follows: The inner solenoid has an internal radius of one inch and is fabricated of 10 mil copper straps 0.5 wide. 10 mil thick insulation is applied between. the outer and innersolenoids. The space between adjacent helices is about 0.3 inch. The solenoids are eight inches long, each having ten turns, substantially. The applied voltage for C27, a 200 microfarad capacitor is 5 kv. The potential on C25, also a 200 microfarad capacitor, is not critical but is limited to 5 kv. so as to not exceed the breakdown voltage of the solenoid insulation. Any value of longitudinal flux due to solenoid 13 augments the comever, and any value between 1 and 1000 microns of mer-' cury is suitable, although gas at an intermediate pressure of about 200 microns of mercury is more easily ionized than gas at extremely low or high pressures, as is well known in the art.

In order to utilize the very high intensity illumination of such discharges, a window 30 is provided in the outer solenoid 15 and a vitreous Window 32 is provided in the Wall of container 11. j

Container purging means 12 and selected gas source and admitting means 14 are connected by ducts and associated valves with the discharge tube;

It has been found that a device in accordance with the foregoing provides an all-metal surfaceto the discharge which eliminates breakage and contamination; it' allows one to produce an axial magnetic field entirely in the gas and therefore closely coupled with the discharge, and it permits precision timing of discharges.

Although the foregoing has described a specific embodiment of a discharge vessel in accordance with this invention, it is understood that such embodiment is for purposes of explanation and that other embodiments may be constructed in accordance with the spirit of this invention. Therefore, it is understood that this invention is to be considered limited only by the appended claims taken in view of the prior art.

What is claimed is:

1. A high energy gaseous discharge device comprising an elongated metal envelope, a main discharge electrode supported on and connected to an end wall of said envelope, a second main discharge electrode insulatingly supported in the opposite end wall of said envelope, at first helical winding of high conductive ribbon material spaced from lateral walls of said container and supported symmetrically about the median line between said electrodes and having its ends connected to a corresponding one of said electrodes, at second helical winding of ribbonlike metallic material supported exteriorly of said first helical winding and insulatingly supported thereon in staggered relation with the turns thereof; magnetic field generating electrical potential means, and a switch, means 4 2,803,772

'4 electrically connecting in series said magnetic field generating electrical potential means, said switch, said first helical winding and said insulated electrode for establishing a magnetic field parallel to the median line between said electrodes; a plasma generating high energy high potential source of electrical energy, a second switch, means electrically connecting in series said plasma generating high energy high potential "source of electrical energy, said second switch and said insulated electrode. 2. A high energy gaseous discharge device comprising an elongated envelope for containing a selected gas, a pair of main discharge electrodes spacedly supported in said envelope, a cylindrical metal shell spaced from and supported symmetrically about the median line between the electrodes, said metal shell comprising an inner solenoid of flat metallic ribbon and an outer solenoid insulatingly supported over the inner solenoid and having its turns staggeredwith respect to the turns' of the inner ing an envelope, a pair of main discharge electrodes supported in opposition in said envelope, a metallic shell symmetrically disposed around and spaced from the discharge path between said electrodes, said metallic shell comprising a first element of spaced helical turns of metallic material and a second element of spaced helical turns of metallic material insulatedly supported in superposition outside said first element and with the turns overlapping the gap between the turns of the first element.

References Cited in the file of this patent UNITED STATES PATENTS 2,266,411 Clavier Dec. 16, 1941 2,543,227 Buckingham Feb. 27, 1951 Webster e Aug. 20, 1957 

